Sensor system and reverse clamping mechanism

ABSTRACT

A sensor system and a reverse clamp is provided. The reverse clamp may include a back portion, a first arm, and a second arm. The first and second arm extending from the back portion to form an opening configured to receive a cylindrical arm.

PRIORITY AND CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. Ser. No. 12/796,233filed Jun. 8, 2010, which is a continuation-in-part of U.S. applicationSer. No. 12/474,911 filed on May 29, 2009, all of which are incorporatedherein in their entirety by reference.

BACKGROUND

1. Field of the Invention

The present application is generally related to sensor system and areverse clamp.

2. Description of Related Art

Optical sensing systems require precise calibration and alignment.However, many sensors utilize fasteners to mount components such assensors or illumination sources into a sensor structure. As such, thetightening of the fasteners may not be consistent for each sensor orperson. Inherent inaccuracies can be introduced between sensors evenduring the alignment and calibration processes due to torque variationin the fasteners.

In view of the above, it is apparent that there exists a need for animproved sensor system.

SUMMARY

In satisfying the above need, as well as overcoming the enumerateddrawbacks and other limitations of the related art, the presentapplication provides a sensor system with a sensor, a laser source, anda mounting structure. The sensor being fixed to the mounting structureusing a reverse clamp and a cylindrical arm.

In another aspect of the application, a reverse clamp is provided. Thereverse clamp includes a back portion, a first arm, and a second arm.The first and second arms extend from the back portion to form anopening configured to receive the cylindrical arm. For example, the backportion, the first arm, and the second arm form an interference fitbetween the opening and the cylindrical arm in a resting state andwherein the first arm and the second arm flex such that the openingmatches a diameter of the cylindrical arm in a flexed state.

Further objects, features and advantages of this application will becomereadily apparent to persons skilled in the art after a review of thefollowing description, with reference to the drawings and claims thatare appended to and form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a sensor system in accordancewith one embodiment of this application;

FIG. 2 is a block diagram illustrating a sensor system including astructured light projector;

FIG. 3 is a block diagram of a sensor system illustrating the opticalelements of the laser sources and sensor;

FIG. 4 is a block diagram illustrating a sensor system including a moiréfringe projector;

FIG. 5 is a block diagram illustrating a sensor system including a dualsensor configuration;

FIG. 6 is a block diagram illustrating one embodiment of a system formeasuring features with the disclosed sensor implementations;

FIG. 7 is a block diagram illustrating one embodiment of a system formeasuring wheel alignment with the disclosed sensor implementations;

FIG. 8 is a side view of one embodiment of a system for measuring wheelalignment with the sensor implementation of FIG. 5;

FIG. 9 is a front view of a laser pattern projected onto a tire for oneembodiment of a system for measuring wheel alignment;

FIG. 10 is a front view of a laser pattern projected onto a tire for oneembodiment of a system for measuring wheel alignment;

FIG. 11 is a front view illustrating various laser patternimplementations projected onto a tire for one embodiment of a system formeasuring wheel alignment;

FIG. 12 is a flow chart illustrating a method for dynamic imageprocessing window adjustment;

FIG. 13 is a flow chart illustrating a method for dynamic identificationof laser lines;

FIG. 14 is a block diagram of a system illustrative of oneimplementation of the controllers, processors, or modules in the instantapplication;

FIG. 15 is a top view of a mounting structure for a sensor system;

FIG. 16 is a front view of a sensor system;

FIG. 17 is a perspective view of a portion of the sensor system in FIG.16;

FIG. 18 is a perspective view of another portion of the sensor system inFIG. 16;

FIG. 19 is a top view of a reverse clamp;

FIG. 20 is a side view of the reverse clamp in FIG. 19;

FIG. 21 is a top view of a reverse clamp;

FIG. 22 is a side view of the reverse clamp in FIG. 21;

FIG. 23 is a front view of the reverse clamp in FIG. 21; and

FIG. 24 is a flowchart illustrating a process for generating a reverseclamp.

DETAILED DESCRIPTION

Referring now to FIG. 1, a system embodying the principles of thepresent application is illustrated therein and designated at 10. Thesystem 10 includes sensor 12, a first laser source 14, a second lasersource 16, and a mounting structure 18.

The sensor 12 may comprise a camera including receiving optics and adetector such as a CCD or CMOS array. Accordingly, the sensor 12 has afield of view that projects outwardly from the camera and a range offocus that is defined by the receiving optics of the sensor. The fieldof view and depth of focus define a sensing volume of the sensor 12. Thefirst laser source 14 may project one or more laser lines onto anobject. If more than one laser line is projected from the first lasersource 14 the lines may be parallel to one another. In addition, thelaser lines may be equally spaced with respect to each other. The firstlaser source 14 is oriented at an angle relative to the sensor such thelaser lines intersect the field of view to define the sensing volume. Inone configuration, the laser lines may be projected such the centerlaser line intersects the center of the sensing volume. Alternatively,if there is an even number of laser lines, the middle two laser linesmay be approximately an equal distance from the center of the sensingvolume.

The sensor 12 and the first laser source 14 may both be attached to themounting structure 18. The mounting structure 18 may be an opticalbench, tube, or other rigid form. The mounting structure 18 may be madefrom a material with a low coefficient of expansion so that therelationship between the sensor 12 and the first laser source 14 is heldconstant across a wide temperature range. Alternatively, the mountingstructure 18 may include a number of temperature sensors to compensatefor expansion of the mounting structure material. The mounting structure18 may be formed from a number of materials including but not limited tosteel, invar, aluminum, or other industrial materials. For example, themounting structure 18 may be an I-tube (shown as reference numeral 1510in FIG. 15). As such, the mounting structure 18 provides both passivethermal management as well as provides a linear response. The linearresponse without hysterisis enables accurate active thermalcompensation.

The sensor 12 and the first laser source 14 may be factory alignedrelative to one another. For example, the sensor 12 and first lasersource 14 may be mounted onto the mounting structure 18 with the use ofvarious fixtures to control the alignment and/or relative position ofthe sensor 12 and first laser source 14. In addition, the sensor 12 andfirst laser source 14 may be mounted to a precision stage, for examplethrough the mounting structure 18. The precision stage may include aknown target. The known target may be moved throughout the sensingvolume by the precision stage such that the relationship between thesensed position of the target can be calibrated throughout the sensorvolume. The calibration can be stored in the sensor as various sensorsystem model parameters including sensor parameters, laser sourceparameters, etc.

Based on the calibration, the relationship between the sensor 12 and thefirst laser source 14 is known and triangulation may be used todetermine the distance from the sensor 12 to a position where a laserline intersects a feature in the sensing volume. As such, the positionof the feature relative to the sensor 12 can be determined based on thefactory calibration regardless of the orientation or positioning of thesensor 12. Further, a system including many sensors may be formed bydetermining the position and orientation of each sensor relative to amaster coordinate space. This may be done for larger systems by using alaser tracker or theodalites to determine the position and orientationof the sensors directly or by using such devices to determine theposition and orientation of a target in the sensing volume thendetermining a transform between the sensor coordinate space and themaster coordinate space.

A second laser source 16 may also be provided. The second laser source16 may be a laser projector such as a structured light projector or amoiré fringe projector. The second laser source 16 may be mounted to themounting structure 18 or alternatively may be mounted independently ofthe mounting structure 18. If the second laser source 16 is mounted onthe mounting structure 18, the position and orientation of the secondlight source may be factory calibrated similar to the first laser source14. However, often times the geometry of the part or the tooling wherethe part is to be measured may present certain environmental constraintsthat would limit the effectiveness of the second laser source 16 beingmounted to the mounting structure 18. In this scenario, a known targetmay be positioned into the sensing volume and the position of the knowntarget to the sensor may be determined based on a triangulation of thelaser line with the sensor. For example, the laser line may be projectedon a flat surface and the position and orientation of the surfacedetermined based on the position of the laser stripe within the field ofview of the sensor. The second set of lines may then be projected ontothe surface and the orientation and position of the second laser sourcemay be determined based on the projected line pattern on the surface.For example, the spacing and angle of an array of line stripes formed onthe surface intersect with the laser stripe from the first laser source14. The intersection points between the laser stripe and the patternfrom the second laser source 16 can be used to determine the positionand orientation of the second laser source 16.

Therefore, the second laser source 16 may be a structured lightprojector, as depicted in FIG. 2. As discussed, the detector 12 iscalibrated with respect to first laser source 14. As such, these twocomponents work together using triangulation principles. The anglebetween the first laser source 14, thus the laser line, and the opticalaxis of the sensor are used to determine the distance and location offeatures on the surface 20. In, addition the second laser source 16projects a series of lines onto the surface 20. The series of lines 21from the second laser source 16 may be oriented orthogonal to the lineor lines from the first laser source 14. The intersection of the line orlines from the first laser source 14 is used to determine the surfaceposition of the series of lines 21 on the surface from the second lasersource 16. The line 22 from the first laser source 14 may as a referencefor the projected pattern from the second laser source 16. The surfaceis then modeled using a camera/optics model. The camera/optics model maybe generated based on taking a few field calibration images once thesensor is finally mounted using a flat surface at a number of distancesfrom the sensor. Accordingly, the second laser source 16 can be mountedseparately from the sensor 12 and first laser projector 14, and fieldcalibrated, as described above.

The mechanics of the sensor system of FIG. 1 are further explained withrespect to FIG. 3. The keystoning effect of the structured light patternincreases the depth sensitivity of the measurement. Therefore,projection angle (theta) of second laser source 16 should be designed tobe different than the receiving angle (phi) of the sensor 12. Forexample, the projection angle may be 10 to 15 degrees different than thereceiving angle. To facilitate the key stoning effect, the projectionoptical system 24 of the laser projector 16 may include two lenses 26,28. The additional lens 28 may be used to vary the magnification betweenthe receiving optic 30 and the projection optical system 24.Specifically, the projection optical system 24 may have 1.5-3 times themagnification of the receiving optic 30 within the sensing volume.Although, other ratios may be used, this may provide particular benefitsfor many industrial applications.

Each of the first and second laser sources 14, 16 and the detector 31may be in communication with the sensor controller 29. The sensorcontroller 29 may independently control the time and intensity of eachlaser source 14, 16. In addition, the sensor controller 29 controls theacquisition and integration time of the detector 30. The sensorcontroller 29 may alternate the projection of the first set of laserlines from the first source 14 and the second set of laser lines fromthe second laser source 16. In addition, the detector 31 may besynchronized with the projection of the first and second laser sources14, 16 to capture the first set of laser lines from the first lasersource 14 in the first image and the second set of laser lines from thesecond laser source 16 in a second image.

The second laser source 16 may also be a moiré fringe projector, asillustrated in the system 410 of FIG. 4. The moiré fringe projector mayemit two wavelengths of laser beams that interfere, thereby projecting amoiré fringe pattern 32 onto the surface 20. The moiré fringe pattern 32is like a topographical map with each ring of the fringe patternequating to a different distance from the second laser source 16. Themoiré fringe pattern 16 includes alternating rings of light rings 38 anddark rings 40 that tend to have a sinusoidal profile. Again, the line 22acts as a reference relative to the distance of each of the rings.

Another embodiment of the sensor system is illustrated in FIG. 5. Thesensor system 510 includes a first sensor 511, a second sensor 512, anda laser source 514. The first sensor 511 and second sensor 512 areattached to a mounting structure 518. The first sensor 511 and secondsensor 512 may be CCD, CMOS, or other similar sensors including otherfeatures, such as a sensor controller, as described with regard tosensors of the previous embodiments. The laser source 514 is alsoattached to the mounting structure 518 and is configured to project alaser pattern 534 onto an object. The laser pattern may be any of thepatterns described above, or more specifically, may include a series oflines that are pre-calibrated relative to each of the first sensor 511and second sensor 512. The pre-calibration may be a factory calibrationas described relative to the previous embodiments.

The sensor system 510 has a sensor axis 520 that is substantiallyperpendicular to the optical axis 532 of the laser source 514. A firstsensor 511 is oriented at an angle relative to the sensor axis 520 thatis slightly less than the second sensor 512. For example, the firstsensor 511 may have an optical axis 524 that is oriented at a 17° anglerelative to the sensor axis 520. Further, by way of example, the secondsensor 512 may have an optical axis 528 that is oriented at a 22° anglerelative to the sensor axis 520. As such, the first sensor 511 has afield of view denoted by reference number 526 that intersects with alaser projection 534 to form a sensing volume 521. The axis of the laserprojection 534 may be orthogonal to the sensor axis 520 and may be inplane with the sensor optical axes 528 and 524. Similarly, the secondsensor 512 has a field of view 530 that intersects with the laserprojection 534 to form a second sensing volume 522. The first and secondsensor 511 and 512 are oriented such that the first sensing volume 521and the second sensing volume 522 form a contiguous sensing volume 523.

The first sensing volume 521 slightly overlaps with the second sensingvolume 522 to form the contiguous sensing volume 523. The sensing volume521 is closer to the mounting structure and sensing volume 522 and mostof the sensing volume 521 does not overlap with the sensing volume 522,and similarly most of the sensing volume 522 does not overlap withsensing volume 521. For ease of illustration, the sensing volumes areshown as squares. However, it is clear that the first sensing volume 521and second sensing volume 522 would have an actual 3-D shape formed bythe intersection of the first field of view 526 with the laserprojection 534 and the second field of view 530 with the laserprojection 534, respectively. This shape would, of course, be expandingas the distance increases relative to the sensor or projector and mayhave curved outer regions based on the effects of the optical system. Assuch, the first sensor 511 and the second sensor 512 work togetherthereby greatly increasing the depth of field which can be analyzedwhile providing sufficient resolution for most applications. Further, itis also clear that similar to the previous embodiments, a second lasersource may also be provided and oriented to project a laser pattern tointersect with the first and second sensing volumes 521, 522. Asdiscussed above, the second laser source may be attached to the mountingstructure or mounted independently

In FIG. 6, a measurement system 610 including an array of sensors 614 isprovided. Each sensor 614 corresponds to a sensor system 10, 410 or 510including any variation or combination thereof described above. Thesystem 610 includes a controller 616 and at least one sensor 614. Theremay be a number of sensors 614 located about a vehicle body or frame 612to measure geometric dimensional deviations at a number of specifiedlocations. Alternatively, a single sensor may be used along with amotion device such that the sensor 614 is able to measure multiplefeatures along the vehicle body 612. For example, the sensor 614 may beattached to a robotic arm that can be manipulated to measure a number offeatures at various locations on the vehicle body 612.

The sensor 614 is in electrical communication with the controller 616 toprovide a set of data for each feature measured. The sensor 614 mayinclude an on board processor to analyze the image data and generatefeature data, for example indicating the position and orientation offeature. The feature data may be communicated to the controller 616. Thesensor 614 may communicate with the controller 616 over a number ofwired or wireless communication protocols including but not limited toEthernet. The controller 616 includes a microprocessor configured toanalyze the data. In addition, the controller 616 is in communicationwith an alarm system 618 to generate an alert based on the measurementsfrom the sensor 614. The alarm system 618 may comprise a visualindicator such as a flashing light, an audio indicator such as a siren,or both. In addition, the alarm system 618 may comprise a communicationsystem configured to send an email, phone message, pager message, orsimilar alert.

Now referring to FIG. 7, an inspection system 710 is provided for theinspection of wheel alignment of a vehicle. As such, the inspectionsystem 710 includes two sensor systems 712 which may correspond with anyof the sensor systems 10, 410, or 510 including variations described inthe previous embodiments or combinations thereof. However, forillustrative purposes, the system 710 will be described further withregards to the implementation of the sensor system 510 shown in FIG. 5.As such, the inspection system 710 includes a left sensor 714 thatprojects a laser pattern 726 onto a left side of tire 728. Similarly,inspection 710 includes a right sensor 716 that projects a second laserpattern 724 onto the right sidewall of the tire 728. Accordingly, theleft sensor 714 and the right sensor 716 may determine the position andorientation of both the left sidewall of the tire and right sidewall ofthe tire 728 to determine an overall position and orientation of thetire 728.

The system 710 may be duplicated for each tire on the vehicle andaccordingly a wheel alignment calculation may be performed includingsuch measurements as toe, camber, pitch, etc., for each wheel of thevehicle. The sensor system 712 may be in communication over acommunication link 720 to a controller 722. The communication link 720may include wired or wireless communications including serialcommunications, Ethernet, or other communication mediums. The controller722 may include a processor, memory, and display to perform a wheelalignment measurement. In addition, the controller 722 may be incommunication with other sensor systems 712 measuring other tires orother controllers configured to inspect the alignment of other wheels onthe vehicle.

Now referring to FIG. 8, a side view of the system 810 is providedillustrating one embodiment of the system in FIG. 7 implementing a dualsensor system described in FIG. 5. The sensor system 812 includes afirst sensor 811 a second sensor 812, and a laser source 814. Each ofthe first sensor 811, the second sensor 812, and the laser source 814may be attached to the mounting structure 818. The field of view of eachof the first and second sensor 811, 812 intersect with the laserprojection 834 of the laser source 814 to form a first and secondsensing volume 821, 822. Further, the first sensing volume 821 andsecond sensing volume 822 overlap to form a continuous system sensingvolume 823. As described above in reference to FIG. 5, the contiguoussensing volume 823 allows for increased sensing range between the sensorsystem 712 and the wheel 728.

This increased sensing range denoted by arrow 840 allows for theaccommodation of a large number of tire models and wheel base vehicles,as well as a large steering angle change during a wheel alignmentinspection. Further, the laser source 814 may include optics thatprovide a 1.5 to 3 times magnification relative to the receiving opticsof both the first sensor 811 throughout the first sensing volume 821 andthe second sensor 812 throughout the second sensing volume 822.

Now referring to FIG. 9, a front view of the tire illustrating oneembodiment of the projected laser pattern is provided. In thisembodiment, the left sensor 714 projects a laser pattern 910 including aseries of parallel lines onto the left-hand sidewall of the tire 728.Similarly, the right sensor 716 projects a pattern 912 including aseries of lines onto the right-hand sidewall of the tire 728. Thepattern may include a first set of lines 914 and a second set of lines916, where the first set of lines 914 are parallel and have equalspacing between each consecutive line. Similarly, the second set oflines 916 may have a set of parallel lines where each consecutive linehas equal spacing. Further, the spacing for the second set of lines 916may be the same as the spacing provided in the first set of lines 914.

Now referring to FIG. 10, the first and second set of lines 914 and 916are described in more detail. The first set of lines 914 may include afirst line 1012, a second line 1014, a third line 1016 and a fourth line1018. Further, the second set of lines may have a fifth line 1020, asixth line 1022, a seventh line 1024 and an eighth line 1026. The linesmay have equal spacing as denoted by reference numeral 1032. However,the distance between the fourth line 1018 and the fifth line 1020 mayinclude a greater spacing 1030 as a line identification. The spacing1030 may be, for example, twice the spacing as between the other lines.This may be easily and effectively accomplished by modifying the gratingof a laser line projection source such that the middle two lines of thegrating are not etched but filled in and therefore do not transmitlight. The additional spacing 1030 may be used to identify specific linenumbers in the pattern.

The first sensing volume 821 of the first sensor and the second sensingvolume 822 of the second sensor may have an overlap region 1010 suchthat the double spacing 1030 may be detected by each of the first sensorand second sensor. Accordingly, the overlap 1010 would be great enoughto show the fourth line 1018 in the first sensing volume 821 and thefifth line 1020 in the second sensing volume 822. However, as can bereadily understood, the array of lines may include more than eight linesand as such, the fourth line 1018 and the fifth line 1020 would berepresentative of the middle two lines of the pattern. Using the changein spacing encodes the line pattern and allows the system to easilyidentify the middle two lines, thereby identifying each line within eachsensing volume. After identifying each line, the relationship betweenthe position of the object, in this case the wheel 728 may be determinedusing a sensor model and the predetermined calibration parameters. Thesensor model may include a camera model that accounts for the detectorand optical parameters of the sensor, as well as, a laser source modelthat accounts for the laser pattern and projection objects. Further, thesensor model and laser source model may be linked by the predeterminedcalibration parameters to provide 3D point cloud data on the object.

Now referring to FIG. 11, additional embodiments are provided foridentifying each line in the pattern 912. In one embodiment a secondlaser line 1110 may be provided orthogonal to the series of laser linesfrom a second laser projector. Alternatively, a unique symbol 1112, suchas a crosshair, may be provided in addition to the series of lines thatmay be used to identify each of the lines in the series based on aspacial relationship. In another alternative, each of the middle twolines may have a mark 1114, 1116, such as a cross tick where the crosstick 1114 on the first set of lines 914 is on one side and the crosstick 1116 of the second set of lines 916 is on an opposite side. Assuch, each of the cross ticks is distinguishable and may be used toidentify each of the lines in the series of lines based on the spacialrelationship. In yet another alternative, the spacing between the linesmay vary such that the number of each line may be identified based on avaried spacing relationship between one or more of the consecutivelines. In one example, a double line 1118 may be provided. The two linesmay be provided closely together uniquely identifies one line in theseries of lines and then each of the other lines may be identified by aconsecutive spacial relationship. Further, other identifyingcharacteristics may be provided for encoding the series of consecutivelines including other various unique marks, or line spacing, linethicknesses, or line orientation.

Now referring to FIG. 12, a method for dynamic image processing windowadjustment is provided. A method 1200 starts in block 1210. In block1210, a laser source projects a pattern onto a feature and an image isacquired of the pattern intersecting the feature. In one implementation,the pattern may be the parallel lines 912 in FIG. 9. In block 1212, thelaser signal pixels are extracted from the image. As such, each of thepixels along the line may be transformed into a line intensity profile.As such, a reference line is defined that is substantially orthogonal tothe series of laser lines and may be acquired with temporal offset. Alaser line profile is determined by adding the intensity valueorthogonal to the reference line after correction for sensor and laserprojection distortions by a camera and/or laser projection model. Inblock 1214, high points are identified in the laser profile. Processingzones are computed based on the high points in the profile, as denotedby block 1216. Finally, processing zones are applied and 3D point clouddata is extracted based on general triangulation principles.

Referring to FIG. 13, a method for the dynamic identification andassignment of laser lines is provided. The method 1300 starts in block1310. In block 1310, the laser is projected onto the feature and animage is acquired. In block 1312, the laser signal pixels are extracted.The marker zones in the laser lines are identified as denoted by block1314. The laser line data is projected on to a reference line, athreshold is applied to integrated projected values to identify nodespoints on the laser lines. The node points along the reference line arethen extracted. The reference line may represent the mean location onthe object being measured. The spacing between nodes are then used toidentify line numbers. In one exemplary, the numbering will start fromthe center where we have higher spacing relative to its immediateneighbors. In block 1316, the laser line numbers are assigned based onthe marker zones.

As such, it is understood that the method shown in FIGS. 12 and 13 maybe utilized together in a single process. For example, the marker zonesmay be identified 1314 and laser line numbers assigned 1316 in betweenstep 1216 and the point cloud data being extracted. Further, the abovedescribed methods may be performed by the sensor controller and as suchthe point cloud data may be transmitted from the sensor to the systemcontroller. Alternatively, the system controller may be utilized forimplementing the methods.

Referring to FIG. 15, the mounting structure 18 may be an I-tube 1510.The I-tube includes a tube portion 1512 with an I-beam 1514. Walls 1516extend beyond the I-beam 1514 and form a recess 1520. The laser sourceand detectors may be mounted in the recess 1520 to the I-beam 1514. Inaddition, the I-tube may include cooling fins 1518 to increasedissipation of heat. The I-tube 1510 may be formed from a number ofmaterials including but not limited to steel, invar, aluminum, or otherindustrial materials. The I-tube 1510 may include a number oftemperature sensors to compensate for expansion of the I-tube material.As such, the I-tube 1510 provides both passive thermal management aswell as provides a linear response. The tubular shape and I-beam limitexpansion in directions other than along the length of the tube. Thelinear response without hysterisis enables accurate active thermalcompensation.

Now referring to FIG. 16, a sensor system is shown that may furtherutilize an I-tube configuration. The sensor system 1610 includes acamera 1612 and a laser source 1628. The camera 1612 and the lasersource 1628 may be of the type described with regard to the otherembodiments provided herein. The sensor structure 1613 may include sidewalls 1616 corresponding to the walls 1516 of the I-tube structure inFIG. 15. Further, the sensor structure 1613 also includes a cross beamor I-beam 1614 corresponding to the I-beam 1514. Further, the cross beam1614 and walls 1616 form a recess 1620 corresponding to recess 1520 inFIG. 15. The camera 1612 is mounted to the sensor structure 1613 suchthat it is rotatable about an axis 1638 that is perpendicular to theside walls 1616. In one implementation, the camera 1612 may be mountedto a mounting plate 1630, for example, using fasteners, adhesive, orother fastening methods. The mounting plate 1630 may include a recess toreceive a pin 1632. Pin 1632 extends from a mounting plate 1630 into aopening in the side wall 1616. The pin 1632 may be a cylindrical pinwith the central axis in alignment with line 1638 allowing the mountingplate 1630 to rotate about line 1638. In addition the mounting plate1630 may include a cylindrical arm 1634 extending from the mountingplate 1630. For example, the cylindrical arm 1634 may have a centralaxis in alignment with line 1638 allowing the camera 1612 to rotateabout axis 1638. The cylindrical arm 1634 is received by a reverse clamp1636. In addition, the camera may be mounted towards the center of thestructure 1613 as such an opening 1622 may be provided so that thecamera 1612 may partially extend through beam 1614.

The reverse clamp 1636 may form an interference fit with the cylindricalarm 1634. Accordingly, as the reverse clamp is expanded, the cylindricalarm 1634 is allowed to rotate and as such the camera 1612 may alsorotate. However, in its normal state, clamp 1636 engages cylinder 1634in an interference fit preventing any rotation of the camera 1612 or themounting plate 1630.

The laser source 1628 is mounted to the sensor structure 1613 such thatit is rotatable about an axis 1648 that is perpendicular to the sidewalls 1616 and parallel to axis 1638. In one implementation, the lasersource 1628 may be mounted to a mounting plate 1640, for example, usingfasteners, adhesive, or other fastening methods. The mounting plate 1640may include a bore to receive a pin 1642. Pin 1642 extends from amounting plate 1640 into a opening in the side wall 1616. The pin 1642may be a cylindrical pin with the cylindrical axis in alignment withline 1648 allowing the mounting plate 1640 to rotate about line 1648. Inaddition, the mounting plate 1640 may include a cylindrical arm 1644extending from the mounting plate 1640. For example, the cylindrical arm1644 may have a central axis in alignment with line 1648 allowing thelaser source to rotate about axis 1648. The cylindrical arm 1644 isreceived by a reverse clamp 1646. In addition the laser source 1628 maybe mounted towards the center of the structure 1613 and, as such, anopening 1626 may be provided so that the laser source 1928 may partiallyextend through beam 1614.

The reverse clamp 1646 may form an interference fit with the cylindricalarm 1644. Accordingly, as the reverse clamp 1646 is expanded, thecylindrical arm 1644 is allowed to rotate and, as such, the laser sourcemay also rotate. However, in its normal state clamp 1646 engagescylinder 1644 in an interference fit preventing any rotation of thelaser source 1628 or the mounting plate 1640.

The laser source 1628 may have a optical axis that is in plane with theoptical axis of the camera 1612 as denoted by line 1658. The mountingplate 1640 is in communication with a base of 1652 of the reverse clamp1650 through flex plate 1654. As such the angle of the base 1652 and,thereby, the angle of the laser source 1628 may be adjusted by applyingpressure to the base 1652 causing the flex plate 1654 to bend or flex.

Further, a reverse clamp 1656 is provided in an interference fit withthe housing of the laser source 1628 the arms 1656 of the reverse clamp1650 engage the housing of the laser source 1628, in normal state.However, in an expanded state, force may be applied to the arms 1656thereby allowing the laser source 1628 to be rotated or moved from thereverse clamp 1650. In addition, a circuit 1660 including a controllerwith a processor can be mounted to the sensor structure 1613, forexample, the I-beam 1614. In this scenario, the processing electronicscan be integrated directly into the sensor system 1610 for a convenientonboard processing.

A more detailed view of the camera 1612 is provided in FIG. 17. Themounting plate 1630 may be implemented in multiple pieces for examplemounting bracket 1631 and mounting bracket 1635. In this examplemounting bracket 1631 is mounted to the camera 1612 through fasteners1730 and 1732. Similarly, bracket 1635 may be mounted to the oppositeside of the camera 1612 by fastener 1722 and 1724. As such, the pin 1632would extend into both the wall 1616 and the bracket 1631. Similarly,the cylindrical arm 1634 would extend from bracket 1635 and be receivedby the reverse clamp 1636. In addition, walls 1616 may include fins 1758corresponding to cooling fins 1518 of FIG. 15. A mounting clamp 1760 mayengage the fins 1758 to secure the sensor system to a inspectionstructure. In addition, the camera may include electronics 1710 and alens 1720. If the electronics 1710 require additional space a opening1752 may be formed in wall 1750. Wall 1750 corresponds to wall 1512 inFIG. 15. The size of the openings 1752 and 1626 are generally minimizedto preserve the structural integrity of the sensor structure 1613.Further, the openings may use chamfers or fillets to minimize the spaceof the opening around the camera or laser source.

Referring now to FIG. 18, the laser source 1628 may include a lens 1814to focus a laser. In addition, the mounting plate 1640 may be integrallyformed with the flex plate 1654, the base 1652, and the reverse clamp1656. In addition, the reverse clamp 1656 may include a flange 1812 witha threaded bore. A screw 1810 may be inserted through the threaded boresuch that turning the screw 1810 relative to the flange 1812 exerts aforce on the base 1652. The force bends or flexes the flex plate 1654,adjusting the angle of projection of the laser source 1628.

Now referring to FIGS. 19 and 20, a top view of a reverse clamp isprovided. The reverse clamp 1910 may correspond to reverse clamp 1636and 1646. The reverse clamp 1910 includes a base 1912 and a clampingportion 1914. The base 1912 may include openings for mounting thereverse clamp 1910 to other structures, for example, the sensorstructure 1613. The clamping portion 1914 includes a back portion 1916and two arm portions 1918 and 1920. A gap 1924 may exist between the twoarm portions 1918 and 1920. The back portion 1916 has an inner surface1926 that cooperates with a inner surface 1928 of arm 1918 and innersurface 1930 of arm 1920 to form a generally circular opening. Surface1926 may have a first radius 1940 that is equivalent to the radius 1942of surfaces 1928 and 1930. In this example, the origin of radius 1942 isoffset relative to the origin of radius 1940 causing an interference fitwith a cylinder received into the opening 1922 that has a radius equalto radius 1942 and 1940. As such, if outward pressure is placed on arms1918 and 1920, both arms 1918 and 1920 will flex causing the opening1922 to form a circular opening having a radius substantially equal toradius 1940 and 1942 around substantially the entire of the opening1922. (e.g. except at filets at the center line of the circular openingor at the gap) In this expanded state, a cylinder of a radius equal to1940 and 1942 may be received into the opening 1922. However, when theforce is removed arms 1918 and 1920 will elastically revert causing aconstant hoop stress around the cylindrical arm received into opening1922 by surfaces 1926, 1928 and 1930 cooperatively. The outer surface ofthe arm 1918 and 1920 is defined by a radius 1946. The thickness of arms1918 and 1920 change from the gap 1924 to the back portion 1916 asdefined by radius 1942 and 1946.

The clamping portion 1914 is separated from the base 1912 by a slot2010. The width of the slot 2014 may be determined based on the materialand stress constraints of the arms 1918 and 1920. The slot 2010 extendsfrom the gap 1924 inwardly towards the back portion 1916 far enoughbeyond the center line 2016 of the opening 1922 to disipate the stresscaused by the force from the flexing arms 1918 and 1920 withoutfracturing the material of the clamping portion 1914. As such, the endpoint 2012 of the slot 2010 is located beyond the center line 2016 intothe back portion of the 1916. The stress in the arms 1918 and 1920 isfocused toward the center line 2016 of the circular opening 1922, whenthe reverse claim 1910 is in the expanded state to receive thecylindrical arm. Moving the end point 2012 of the slot 2010 into theback portion 1916 allows better dissipation of the stress due to flexingof the arms 1918 and 1920.

By offsetting the radius 1942 of surfaces 1928 and 1930 from radius 1940of surface 1926 the clamp opens to form a circular geometry the same asthe cylinders received into the opening, while maintaining a constanthoop stress completely or nearly completely (e.g. 300-360 degrees)around the received cylinder in its normal state. Due to theconstruction, the arms 1918 and 1920 are biased to engage the receivedcylinder with surfaces 1928 and 1930 that match the radius of thereceived cylinder thereby forcing the cylinder against surface 1926 ofthe back portion which also has a radius that matches the radius of hecylinder. This unique construction produces a constant hoop stressaround the cylinder cooperatively formed by the surfaces 1926, 1928, and1930. By using the reverse clamping mechanism, the clamping stress isalso consistent regardless of the person positioning of the cylinderwithin the opening of the reverse clamping mechanism. In most clampingmechanisms, positive force is exerted due to a tightening of the clamp.For example, a fastener imarts force on the object being clamped whichis subject to a variation in torque from each person clamping theclamping mechanism. In addition, it prevents creeping that can typicallyoccur due to forces imparted on the clamping surfaces as the clamp istightened. The material of the clamping portion of the reverse clamp maymatch the material of the cylinder received in the opening. The reverseclamp may be made of various material such as aluminum, titanium, orsteel, however, for certain optical sensors 60/61 T6 Aluminum, or 70/75T6 Aluminum may provide desirable characteristics. Accordingly, thereverse clamp may produce a force of between 200-700 newtons, and forthe optical sensors described may be even more desirable in the range of400-500 newtons.

Now referring to FIGS. 21, 22 and 23, the reverse clamp 2110 maycorrespond to reverse clamp 1656. The reverse clamp 2110 is attached toa mounting plate 2111 through a flex plate 2152. The reverse clamp 2110includes a base 2112 and a clamping portion 2114. The clamping portion2114 includes a back portion 2116 and two arm portions 2118 and 2120. Agap 2124 may exist between the two arm portions 2118 and 2120. The backportion 2116 has an inner surface 2126 that cooperates with an innersurface 2128 of arm 2118 and inner surface 2130 of arm 2120 to form agenerally circular opening. Surface 2126 may have a first radius 2140that is equivalent to the radius of surface 2142 of surface 2128 and2130. In this example, the origin of radius 2142 is offset relative toradius 2140 causing an interference fit with a cylinder received intothe opening 2122 that has a radius equal to radius 2142 and 2140. Assuch, if outward pressure is placed on arms 2118 and 2120 from withinthe gap 2142, both arms 2118 and 2120 will flex causing the opening 2122to form a circular opening having a radius substantially equal to radius2140 and 2142 around substantially the entire of the opening 2122. (e.g.except at filets at the center line of the circular opening or at thegap) In this expanded state, a cylinder having a radius equal to 2140and 2142 may be received into the opening 2122. However, when the forceis removed arms 2118 and 2120 will elastically revert causing a constanthoop stress around the cylinder received into opening 2122 by surfaces2126, 2128 and 2130 cooperatively. The outer surface of the arm 2118 and2120 is defined by a radius 2146. The thickness of the arm 2118 and 2120may change from the gap 2124 to the back portion 2116 of the clampingportion 2114 as defined by radius 2142 and 2146.

The clamping portion 2114 may be separated from the base 2112 by a slot2210. The width of the slot 2214 may be determined based on the materialand stress constraints of the arms 2118 and 2120. The slot 2210 extendsfrom the gap 2124 inwardly towards the back portion 2116 far enoughbeyond the center line 2216 of the opening 2122 to disipate the stresscaused by the force from the flexing of arms 2118 and 2120 withoutfracturing the material of the upper portion 2114. As such, the endpoint 2212 of the slot 2210 is located beyond the center line 2216 intothe back portion of the 2116. The stress in the arms 2118 and 2120 isfocused toward the center line 2216 of the circular opening 2122, whenthe reverse claim 2110 is in the expanded state to receive thecylindrical arm. Moving the end point 2212 of the slot 2210 into theback portion 2116 allows better dissipation of the stress due to flexingof the arms 2118 and 2120.

By offsetting the radius 2142 of surfaces 2128 and 2130 from radius 2140of surface 2126 the clamp opens to form a circular geometry the same asthe cylinders received into the opening while maintaining in its normalstate a constant hoop stress completely or nearly completely (e.g.300-360 degrees) around the received cylinder. Due to the construction,the arms 2118 and 2120 are biased to engage the received cylinder withsurfaces 2128 and 2130 that match the radius of the received cylinderthereby forcing the cylinder against surface 2126 of the back portionwhich also has a radius that matches the cylinder. This uniqueconstruction produces a constant hoop stress around the cylindercooperatively formed by the surfaces 2126, 2128, and 2130.

In addition the mounting plate 2150 may be integrally formed with a flexplate 2152 and the reverse clamp 2110. In addition the reverse clamp2110 may include a flange 2154 with a threaded bore. A screw may beinserted through the threaded bore such that turning the screw relativeto the flange 2154 exerts a force on the base 2112 thereby bending orflexing the flex plate 2152 and adjusting the angle of the base 2112relative to the mounting plate 2150.

Now referring to FIG. 24 a process 2400 for generating a reverse clampis provided. In block 2410, the clamping diameter is defined. In block2412, the clamping offset is estimated. The clamping offset relates tothe eccentricity of the clamping arm diameter and in addition definesthe amount of flex each arm will require to form an opening equal to theradius of the cylinder, as well as, the hoop stress imparted on thereceived cylinder. In block 2414, the clamping arm contour geometry isestimated. In block 2416, the material is defined based on the desiredhoop stress and the required flex. The reverse clamp may be formed ofaluminum, titanium, or other similar materials. In block 2418, a finiteelement analysis is performed to calculate the force generated by theclamp when the arms are open to the clamping diameter. Accordingly, thearms may impart a force on the cylinder of between 200-700 newtons. Inblock 2420, it is determined if the localized stress in the clampexceeds the yield stress of the material and if the strain is below theelastic limit for the material. If the localized stress is below theyield stress and the strain is below the elastic limit, the methodfollows line 2426 to block 2428 and the process ends. Alternatively, ifthe localized stress is not below the yield stress or the strain is notbelow the elastic limit, the method follows line 2424 to block 2412where the clamping offset is re-estimated based on the results of thefinite element analysis in block 2418.

Further, it should be noted that once the parameters for the reverseclamp have been defined, the reverse clamp may be manufactured accordingto a unique process. The reverse clamp including the back portion, thefirst arm, the second arm and the base may be formed from a unitaryblock of material. The opening may be formed by boring and milling, forexample, using a CNC machine. The opening may be formed as describedabove with respect to FIGS. 19-23. the gap may be formed in the block toproduce two arms, for example, by milling into the opening. Then, theouter surface of the arms may be formed by milling and the slot may becut to form the arms and the base portion. Forming the reverse clamp inthis manner provides a high clamping force required for opticalapplications and a constant hoop stress substantially entirely aroundthe cylindrical arm received within the opening.

Any of the modules, controllers, servers, or engines described may beimplemented in one or more computer systems. One exemplary system isprovided in FIG. 14. The computer system 1400 includes a processor 1410for executing instructions such as those described in the methodsdiscussed above. The instructions may be stored in a computer readablemedium such as memory 1412 or a storage device 1414, for example a diskdrive, CD, or DVD. The computer may include a display controller 1416responsive to instructions to generate a textual or graphical display ona display device 1418, for example a computer monitor. In addition, theprocessor 1410 may communicate with a network controller 1420 tocommunicate data or instructions to other systems, for example othergeneral computer systems. The network controller 1420 may communicateover Ethernet or other known protocols to distribute processing orprovide remote axis to information over a variety of network topologies,including local area networks, wide area networks, the internet, orother commonly used network topologies.

In an alternative embodiment, dedicated hardware implementations, suchas application specific integrated circuits, programmable logic arraysand other hardware devices, can be constructed to implement one or moreof the methods described herein. Applications that may include theapparatus and systems of various embodiments can broadly include avariety of electronic and computer systems. One or more embodimentsdescribed herein may implement functions using two or more specificinterconnected hardware modules or devices with related control and datasignals that can be communicated between and through the modules, or asportions of an application-specific integrated circuit. Accordingly, thepresent system encompasses software, firmware, and hardwareimplementations.

In accordance with various embodiments of the present disclosure, themethods described herein may be implemented by software programsexecutable by a computer system. Further, in an exemplary, non-limitedembodiment, implementations can include distributed processing,component/object distributed processing, and parallel processing.Alternatively, virtual computer system processing can be constructed toimplement one or more of the methods or functionality as describedherein.

Further the methods described herein may be embodied in acomputer-readable medium. The term “computer-readable medium” includes asingle medium or multiple media, such as a centralized or distributeddatabase, and/or associated caches and servers that store one or moresets of instructions. The term “computer-readable medium” shall alsoinclude any medium that is capable of storing, encoding or carrying aset of instructions for execution by a processor or that cause acomputer system to perform any one or more of the methods or operationsdisclosed herein.

As a person skilled in the art will readily appreciate, the abovedescription is meant as an illustration of the principles of thisinvention. This description is not intended to limit the scope orapplication of this invention in that the invention is susceptible tomodification, variation and change, without departing from spirit ofthis invention, as defined in the following claims.

1. A reverse clamp comprising: a back portion; a first arm extendingfrom the back portion; and a second arm extending from the back portion,the first and second arm cooperating to form an opening configured toreceive a cylindrical arm.
 2. The reverse clamp according to claim 1,wherein the back portion has a first surface configured to engage thecylindrical arm, the first arm having a second surface configured toengage the cylindrical arm, and the second arm having a third surfaceconfigured to engage the cylindrical arm.
 3. The reverse clamp accordingto claim 2, wherein the first, second, and third surfaces cooperate forprovide a constant hoop stress around substantially the entirecylindrical arm.
 4. The reverse clamp according to claim 2, wherein theback portion, the first arm, and the second arm form an interference fitbetween the opening and the cylindrical arm in a resting state andwherein the first arm and the second arm flex such that the openingmatches a diameter of the cylindrical arm in a flexed state.
 5. Thereverse clamp according to claim 2, wherein the first surface has afirst radius, the second surface has a second radius, the third surfacehas a third radius, a first origin of the first radius being offsetrelative to a second origin of the second and third radius, wherein thefirst, second and third radii are equal.
 6. The reverse clamp accordingto claim 1, wherein a gap is formed between the first arm and the secondarm, the reverse clamp including a base attached to the back portion, aslot being formed between the base and the first and second arms, theslot extending from the gap into the back portion, an endpoint of theslot being located beyond a center line of the opening into the backportion.
 7. A method for manufacturing a reverse clamp comprising thesteps of: providing a unitary block of material; forming an opening inthe block; forming a gap into the opening to produce two arms; andforming a slot to produce a base and a clamping portion.
 8. A method forgenerating a reverse clamp comprising the steps of: defining a clampingdiameter; estimating a clamping offset; estimating a clamping armcontour geometry; defining a material for the reverse clamp; running afinite element analysis to calculate a force generated when arms of thereverse clamp are open to the clamping diameter; and verifying alocalized stress in the reverse clamp does not exceed a yield stress forthe material and that a strain in the clamp is below an elastic limitfor the material.